Blanking out car number plates

I just sat through You Are What You Eat (doesn't McKeith look gaunt and drawn - do you think she's eating properly? ;)), and noticed they greyed out the car number plate of the vicar she was treating. This blanking out of number plates seems to be happening more and more on TV. Is it a legal requirement, is it simply for the person's privacy, or is there some other reason? Anyone know?

Mr Scummy

(By the way I felt really sorry for that poor vicar in YAWTE tonight: McKeith reduced him to tears at one point, showed his mega-dump in extreme close-up and commented on how smelly it was, and so on. It's the first time I've watched YAWTE and by the end I wanted to get up and shake McKeith's scrawny neck - does she always humiliate her victims like this?)
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